1.1 Populations and Ecosystems

Varinder Singh B.

Learning Objectives

• Understand the meanings of a few new, ecological terms.

• Understand the mechanics behind an ‘ecosystem’.

• Understand what a ‘niche’ is.

Success Criteria

• Relate the words to real-life ecosystems.

Ecology – The Study Of...• Ecology is about studying relationships between organisms

and their environment.

ENVIRONMENTThe conditions surrounding an organism. The environment can

be split into living and non-living components.

Black Bear Catskill Mountains, NY

Environment• So, Environment = conditions surrounding an organism.• These conditions are either living or non-living.

LIVING = BIOTICNON-LIVING = ABIOTIC

• Biotic factors can include things such as competition between individuals, predation and disease.

• Abiotic factors can include things such as temperature, rainfall and natural disasters.

Biotic Factors• Competition• Predation• Disease• Availability of food

Abiotic Factors• Temperature• Rainfall• Light• Natural Disasters• Rivers

Ecosystem• An ecosystem is the largest level of organisation we study in

ecology. • It’s an area in which organisms interact with both the

environment and with each other.

<- A Rainforest Ecosystem:The ecosystem is the entire area and what lives within it.The environment includes the conditions.

Two Major Things About Ecosystems:1. There is an energy flow2. Recycling of elements

Energy Flow in an Ecosystem

What is the ultimate source of energy for an ecosystem?Solar Energy

The flow of energy in an ecosystem is as follows:

Solar Energy Chemical Energy

What kind of organisms are responsible for this flow?Plants (Photoautotrophs)

Photosynthesis

Energy Flow in an Ecosystem

The previous slide dealt with the overall flow of energy through an ecosystem, and how it originally enters it.

However, there are other organisms involved as well as plants.

Energy is transferred through trophic levels.

Producer Primary Secondary Tertiary Consumer Consumer Consumer

All energy passing through the ecosystem is eventually returned to it as heat.

Populations• A population is a group of organisms of a SINGLE SPECIES, living

in the same area, that breed together.Groby?

• Boundaries of a population are hard to define. For humans it’s pretty easy, but for insects and migratory birds it can be difficult.

log

1km

another log

Community• A community is all of the populations in the ecosystem.• The populations in the community will be:

– Living together– Interacting with each other– Killing and eating each other

Remember: We’re not just talking about animals. Populations and communities include the plants too.

Anaconda

Ants

Frogs

Bats

Spiders

Birds

Plants

Habitats• Within an ecosystem, there are many areas where organisms

can live. These areas are called habitats.

The type of habitat depends on the species.Mammalian habitats are different from amphibian or bird habitats.

Some habitats overlap.

Microhabitats are small pockets within an ‘ordinary’ habitat.• A python may live on a tree, but the cracks in the bark may be home to woodlice.

Niche• Think of every organism in an ecosystem as having a job there.

• The environment dictates how the organism does it’s job.

A NICHE refers to where an organism lives, and what role it plays within the environment.

All of the biotic and abiotic factors of the environment influence the niche.

The ecological niche of an organism depends not only on where it lives but also on what it does. By analogy, it may be said that the habitat is the organism's "address", and the niche is its "profession",

biologically speaking.Odum - Fundamentals of Ecology - W B Saunders 1959

Example:

Oak trees live in oak woodlands. The oak woodland is the habitat. So if you were writing a letter to an oak tree, you would address the letter to:Sir Deciduous Oak Tree,The Oak Forest,England,U.K.

What do oak trees do? If you can answer that question you know the oak trees "profession" or its ecological niche. Perhaps you think that oak trees just stand there looking pretty and not doing vey much, but think about it.Oak trees:•absorb sunlight by photosynthesis; •absorb water and mineral salts from the soil; •provide shelter for many animals and other plants; •act as a support for creeping plants; •serve as a source of food for animals; •cover the ground with their dead leaves in the autumn.